Polycystic ovary syndrome (PCOS) is the most common reproductive endocrine disease in women of reproductive age. Approximately three-quarters of women with anovulatory infertility have PCOS, thus accounting for approximately one-third of women with secondary amenorrhea and approximately 90% of women with oligomenorrhea. Other consequences of PCOS are hirsutism, markedly increased incidence of recurrent early pregnancy loss, an estimated 11-fold increased risk of myocardial infarction between the ages of 50-61 years, and an increased risk of endometrial cancer at a young age. A consistent finding in women with PCOS is that the ovaries produce abnormally high amounts of androgens. There is good evidence to conclude that elevated androgens interfere with selection of dominant follicles and cause PCOS. Importantly, there is an association between insulin resistance and the androgen excess of PCOS. It is clear that insulin can stimulate ovarian androgen production, but a paradox exists: how can insulin hyperstimulate ovarian thecal androgen production in an insulin resistant woman? One of two hypotheses could explain the seeming paradox. Either the ovarian theca cells are not insulin resistant in insulin resistant women or there are distinct insulin signaling mechanisms regulating glucose metabolism and androgen production in theca cells. The purpose of the proposed studies is to determine if ovarian theca cells are insulin resistant in insulin resistant women, to explore the intracellular signaling mechanisms by which insulin regulates androgen biosynthesis, and to determine if there are differences in the concentrations and/or activities of key molecules mediating insulin action in theca cell from polycystic ovaries. To accomplish these goals, we will measure the sensitivity of skeletal muscle and ovarian theca cell glucose uptake in response to insulin to determine the relative sensitivity of these tissues to insulin in insulin sensitive and insulin resistant women with and without PCOS. We have established a human theca cell culture model in which we can examine the molecular details of insulin signaling. Importantly, increased androgen production and steroidogenic enzyme mRNA over-expression persist in the cultured cells in vitro. We propose to use this model to systematically determine the intracellular signaling pathway for insulin stimulation of CYP 17 activities and mRNA expression and then to compare the concentrations and activities of the signaling molecules between regularly cycling control women and women with PCOS. The results of these studies are expected to yield specific molecular targets for novel therapies to treat women with PCOS.